Low-Coordinated Titanium(III) Alkyl-Molecular and Surface-Complexes: Detailed Structure from Advanced EPR Spectroscopy.

The structure of paramagnetic surface species is notoriously difficult to determine. For TiIII centers related to Ziegler-Natta catalysis, we demonstrate here that detailed structural information can be obtained by advanced EPR spectroscopy and DFT computations, benchmarked on molecular analogs. The hyperfine sublevel correlation (HYSCORE) spectra obtained after reaction with 13 C-labeled ethylene provides information about the coupling with a proton in the first coordination sphere of TiIII as well as significant 13 C hyperfine coupling and thereby allows structural assignment of the surface species.